Process of making photographs



Patented Nov. 30, 1943 PROCESS OF MAKING PHOTOGRAPHS Otto Vierling, Dresden, Germany; vested in the Alien Property Custodian No Drawing. Application May 31, 1940, Serial No. 338,236. In Germany July 5, 1939 3Claims.

In D. S. Patent 2,186,942, there is described a process for making photographs characterized by the use of phototropic matter which under the influence of rays of a certain wave length visibly alter their substantial color orwhich adopt a definite tint on exposing them to light of a certain spectral range and which adopt a color tone difierent from the first one when exposed to light of another spectral range, especially of fulgides as a repeatedly applicable light sensitive material. Instead of the fulgides also compounds of hydrazones are suited for this purpose.

The further development of the above process has shown that the properties of layers for makingsuch photographs may be varied in different direction by the use of mixtures of two or several phototropic substances. It is possible especially to widely ailect and vary the tone and the extent of the color, the sensitiveness, the contrast and the gradation of the pictures.

It is well-known that the phototropic substances have in general a well defined color, which, when excited, changes in a definite manner. For instance the triphenylfulgide in a lionexcited state is yellow, while, when excited, it adopts a red-brown tone. It is quite evident that such colors'do not correspond in most cases to the characteristic color of the picture in photographic printing. As a rule a black and white picture is preferred. Therefore the phototropic layer should show such or a similar feature.

Since phototropic substances of suincient sensitiveness producing. a white and black color change are unknown, it is an object of the present invention to produce a layer approaching such an ideal case by mixing various phototropic substances together.

In analogy to the known monochrome toned photographic prints there is sometimes a demand for phototropic layers producing a definite color tone when energised by light.

For instance a brown-violet color tone may be I obtained in the following manner: Mix the wellknown a-methyl-a,t-diphenylfulgide which is excited from yellow to red with a-methyl-a-phenyl- (o-nitrophenyl) -'iulgide which is excited from yellow to blue-grey. Both components are mixed ina proportion of 1:1. By choosing another ratio of combination, it is possible to obtain a color tone leaning toward red or toward blue, as desired.

The process described in the invention may also be employed for varying the extent of the color tone (except of blackening) of the phototropic layer. By mixing a phototropic substance of great sensitlveness but of small blackening extent with another phototropic substance of little sensitiveness but of great blackening extent a combined layer may be made which incorporates great sensitiveness and great extent of blackens.

In the same way the contrast and above all the curve of gradation of thecombined layer may be influenced.

The combined layers can be made in. various ways. The selected components, if they are available in powdered form, may for instance be mixed in asimple way and dusted, sprayed or applied thinly in any manner upon a support provided with .an adhesive layer. The various components may however also be mixed into a binding substance which is then transferred to a support. The mixing of the components, may either be done in the binding substance itself or the components may be mixed before the binding substance is added to them.

Itis also possible to mix each component separately with a binding substance which for various components may difier, and then mix the various preparations together.

As binding substances are selectedvfor instance gelatine, albuminoils, alginates, cellulose derivatives, artificial resins or similar substances.

The ratio of combination depends on the prevailing requirements. Instead of the process indicated above the combined layer may also be made by superimposing several layers on a support. The pouring is best done successively in such a way that the next layer is applied only after the previous one has hardened to a certain degree. When applying this process it is possible, in addition to varying the concentration of the layers, to vary the color tone by varying the thickness of the layers.

What I claim is:'

1. In a process for making a photographic positive on phototropic material whereby to provide a fugitive print, the steps of illuminating a composite layer of several different fulgides of contrasting color through a negative with light of a certain spectral range which will visibly alter the color of said layer, said layer being adapted to change its color under the influence of and in accordance with the intensity of illumination of said light passing through the negative, and then subjecting the layer to the action of light of a difierent spectral range which will cause the visible appearance of said layer to change back to its original color whereby the positive print produced on said layer by the first illumination is caused to disappear.

2. The process set forth in claim 1 for making 3. The process set forth in claim 1 for making a fugitive photographic positive wherein the phototropic layer is formed of a mixture of several diflerent fulgides to provide a composite layer which will assume a brown-violet color tone when light within a certain spectral range is transmitted onto said layer through the photographic negative of which a positive is to be made.

O'I'IO VIERLING. 

